1. Field of the Invention
The present invention relates to a signal processing apparatus, a signal processing method, and a program. In particular, the present invention relates to a signal processing apparatus, a signal processing method, and a program which enables improvement in quality of communication performed over a transmission path in which signal distortion occurs.
2. Description of the Related Art
There are known signal processing apparatuses that receive an image signal from an external device such as a tuner for receiving a television broadcast signal or the like or a digital versatile disc (DVD) player, subject the received image signal to signal processing, and supply the resultant image signal to a display apparatus such as a cathode ray tube (CRT) or a liquid crystal display (LCD).
Such signal processing apparatuses perform signal processing such as a noise removal process of removing noise from the image signal supplied from the external device, an image conversion process of converting the image signal so that an image to be displayed on the display apparatus will have a higher image quality than an image supplied from the external device, or an image adjustment process of adjusting brightness or contrast of the image to be displayed on the display apparatus.
FIG. 1 is a block diagram illustrating an exemplary structure of a known signal processing apparatus 11.
In FIG. 1, the signal processing apparatus 11 includes a housing 12, connectors 131 to 134, an input selector 14, a signal router 15, connectors 161 to 164, connectors 171 to 173, functional blocks 181 to 183, a connector 19, a remote commander 20, an operation section 21, a system control block 22, and a control bus 23.
In the signal processing apparatus 11, the connectors 131 to 134 are connected to the input selector 14 via signal cables, and the input selector 14 is connected to the signal router 15 via a signal cable. Further, the signal router 15 is connected to the connectors 161 to 164 and the connector 19 via signal cables, and the signal router 15 is connected to the functional blocks 181 to 183 via the connectors 161 to 163 and the connectors 171 to 173. Still further, the input selector 14, the signal router 15, the connectors 161 to 164, and the system control block 22 are connected to one another via the control bus 23.
The housing 12 is a box in the shape of a rectangular parallelepiped, for example. The connectors 131 to 134, the connector 19, and the operation section 21 are provided on the exterior of the housing 12. The housing 12 contains the input selector 14, the signal router 15, the connectors 161 to 164, the connectors 171 to 173, the functional blocks 181 to 183, the system control block 22, and the control bus 23.
The connectors 131 to 134 are parts to which is connected a cable for connecting the signal processing apparatus 11 to an external device (not shown), such as a tuner or a DVD player, that supplies an image signal to the signal processing apparatus 11.
The image signals are supplied from the external devices to the input selector 14 via the connectors 131 to 134. Under control of the system control block 22, the input selector 14 supplies, to the signal router 15, the image signal supplied from the external device connected to one of the connectors 131 to 134.
Under control of the system control block 22, the signal router 15 supplies the signal supplied from the input selector 14 to the functional blocks 181 to 183 via the connectors 161 to 163 and the connectors 171 to 173. Signals obtained as a result of signal processing are supplied from the functional blocks 181 to 183 to the signal router 15, and the signal router 15 supplies the signals obtained as a result of signal processing to a display apparatus (not shown) connected to the connector 19 via the connector 19.
The connectors 161 to 163 and the connectors 171 to 173 can be connected to and detached from each other, and they are used to connect the signal router 15 or the control bus 23 to the functional blocks 181 to 183. To the connector 164, a new functional block or the like to be added to the signal processing apparatus 11 can be connected.
Each of the functional blocks 181 to 183 has a signal processing circuit for performing signal processing such as the noise removal process, the image conversion process, or the image adjustment process. Each of the functional blocks 181 to 183 performs signal processing on the signal supplied from the signal router 15, and supplies the signal obtained as a result of signal processing to the signal router 15.
The connector 19 is a part to which is connected a cable for connecting the signal processing apparatus 11 to the display apparatus for displaying an image outputted from the signal processing apparatus 11.
The remote commander 20 has a plurality of buttons or the like to be operated by a user. When any of the buttons or the like is operated by the user, the remote commander 20 supplies an operation signal corresponding to that user operation to the system control block 22 using infrared rays or the like.
As with the remote commander 20, the operation section 21 has a plurality of buttons or the like to be operated by the user. When any of the buttons or the like is operated by the user, the operation section 21 supplies an operation signal corresponding to that user operation to the system control block 22.
When the operation signal corresponding to the user operation has been supplied from the remote commander 20 or the operation section 21, the system control block 22 controls, via the control bus 23, the input selector 14, the signal router 15, or the functional blocks 181 to 183 so that a process corresponding to the operation signal will be performed.
In the signal processing apparatus 11 having the above-described structure, the image signal is supplied to the signal router 15 via the connectors 131 to 134 and the input selector 14, and the image signal is transferred between the signal router 15 and the functional blocks 181 to 183 via the signal cables.
Recent years have seen an increase in resolution of images, and there is a tendency for the data amount of the image signal to be subjected to signal processing by the signal processing apparatus 11 to increase. The increase in the data amount of the image signal results in the image signal being transferred at a high speed between the signal router 15 and the functional blocks 181 to 183 via the signal cables, for example. When the signal is transferred at a high speed, a problem occurs in the transfer of the signal due to influence of frequency characteristics of the signal cables, cross talk, timing variations (i.e., skew) that occur between parallel signal cables, or the like.
Here, Japanese Patent Laid-Open No. 2003-179821 discloses a signal processing apparatus in which substrates contained in a housing of the apparatus transfer signals therebetween via wireless communication using electromagnetic waves for signal processing.
As in this signal processing apparatus, the signal router 15 and the functional blocks 181 to 183 may transfer signals therebetween via wireless communication using electromagnetic waves, for example. Thus, the problem that occurs when the signals are transferred via the signal cables can be avoided.
However, when the signal router 15 and the functional blocks 181 to 183 transfer the signals therebetween via wireless communication using the electromagnetic waves within the housing 12 of the signal processing apparatus 11, the electromagnetic waves will be reflected by walls of the housing 12 or diffracted by substrates contained in the housing 12, so that multiple transmission paths having different distances (i.e., multipath) will arise. When the signals are transferred over such multiple paths, the signals that have reached a receiver via the multiple paths will be out of phase with each other, resulting in signal interference.
As described above, when the signals are transferred via wireless communication within the housing 12, i.e., when the signals are communicated over transmission paths that cause waveforms of the signals to be distorted because of signal interference, a substrate at the receiving end is unable to demodulate the received signals successfully, resulting in reduction in communication quality.
The above problem occurs not only in the wireless communication within the housing but also in mobile communications via mobile phones, for example. That is, multipath that occurs as a result of the electromagnetic waves being reflected by a structure such as a building causes the signals to be out of phase with each other, resulting in signal interference and reduction in communication quality. Moreover, the above problem is not limited to the wireless communication. For example, when a signal is transferred via a cable, the signal is reflected at an end of the cable and the reflected signal will interfere with the original signal to be transferred, resulting in reduction in communication quality.
As countermeasures against multipath in signal processing using common wireless communication, there are some known methods such as a method of using orthogonal Frequency Division Multiplexing (OFDM) as a modulation scheme, a method of using spread spectrum and rake reception, a method of using multiple antennas, and a method of using a waveform equalizer.
In signal processing for image signals, particularly signals that need to be transferred at a high speed such as uncompressed image signals, it is necessary to reduce delays that occur in signal processing and make the delays uniform. With the use of the above countermeasures against multipath, however, it is difficult to reduce the delays that occur in signal processing or make the delays uniform.
Further, in the case where OFDM is adopted as the modulation scheme, a heavy load is imposed on a device that performs a fast Fourier transform (FFT) process for modulation and demodulation, and such a device may radiate increased amounts of heat, or costs may be increased. Still further, in the case where spread spectrum is used, more rapid signal processing than that for the signals to be transmitted is requisite to achieve high-speed communication, but so rapid signal processing is difficult to achieve, resulting in difficulty in achieving high-speed communication.
Still further, in the case where multiple antennas are used or where the waveform equalizer is used, it is necessary to insert a unique word (UW) in a packet, or a large-scale prediction circuit is requisite for improving the accuracy in predicting a change in transmission characteristics.